Throttling valve



MAQQALBB MMI 11j-192% B. T. WILLISTON THROTTLING VALVE Filed May 15. 1925 NELVIN T. WILISTON, OIF SOMERVILIIE, MNSSACHUSETTS, ASSIGNOR T MANNING,

` & MO0NE, INC., ,0F YORK, N. Y., CORPORATION 01E' NEW 'l'mlslEY.

TJEINTTJLING VALVE.

i ntpnnon'aiea nay'ia, ma. serial ivo; aaaota,

` and resident of Somerville, in the county of Middlesex and @tate of Massachusetts, have invented new land useful improvements in Throttlin Valves, of which the following is a -speci cation.

My invention relates to valvesfor reducing or regulating steam pressures, generally known as throttling valves. Valves of this charactenused as they are to a'ord a con- ,stricted/ passage for' steam, are especially subjected to the erosive action of steam, or steam and water, moving at high velocity, and /as heretofore designed and constructed, have su'ered serious deterioration from this cause, and have therefore been'short-lived in service. rlhrottling A valves ,perform their function by providing a passage between a container of'steam at high pressure to a con tainer of steam at low pressure, by constraining and directing the steam in its flow through the passage in such manner that it expands and thus diminishes its pressure in transit, emerging into the low pressure container at the pressure which is to be maintained therein. lt is understood, of course, that the diderential in ressure is sustained by a constant4 supply o` heat-energy to the high pressure container and-a corresponding consumption of energy in or from the low pressure container, while the throttling valve is in cperation.`

lin order to perform its functions, therefore, the throttling valve must provide adequately by its design for the expansion of steam required to produce the determined pressure-difference, this expansion must take place and the determined lower pressure be reached in the passage bounded by the surface of the closure-member of the valve, and the surface of the aperture in the valve casing iii-which the closure-member operates. Should the steam emerge from this passage at pressure higher thanl that to be maintained in the low-pressure container, leaving inal expansion to be edected therein, the steam 'et will bell on emergence, and act erosive y on the edges of the valve members and 'thereafter on portions of the passagewalls within the aperture. ln the expansion T. Winnis'ron,

passage itself, if this be not so designed as to vinduce flow of steam at allpoints substantially parallel with the surfaces which bound, or form, the passage, nodes andintervening regions of erosive impingement on these surfaces will be' formed-1n the stream of fluid, and will soon aggravate conditions by locally wearing away the surfaces. Such erosion not only degrades the eiciency of the valve as a throttling instrument, but also tends to makethe valveleak when it should be closed tightly.

llf steam contains any water, the erosive ede'ctof its action in a constricted passage,

ist

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orin flovving'past edges or bendsliL the pasi sage, is materially increased. llt is highly desirable, therefore, that a throttlin valve should -provide for free expansion' o steam so as to effect re-evaporation of any included water as promptly as possible.

The objects, therefore, of this invention,

'are to provide a throttling valve with its essential members of such shape and roportion that a throttling passage wil be produced through which expanding fluid will pass, and from which it will emerge in direction always substantially parallel with the walls of the passage, and thus Without inducing the formation of'loci of yerosion withinthe passage, or of erosive belling" at the emergence from the passage; and such that expansion of elastic fluid in the passage will produce the desiredfall in fluid pres4 sure. Another object, closely associated with the foregoing, is to provide unusually extensive surfaces of Contact between the movable closure member of the throttling valve, and

the casing-member which contains it; thisv provision to' be consistent, by reason of the principles o f design, with the substantially straight-flow aperture. A further, though I subordinate, object, concerned with the intake ofelastic fluid by the valve aperture or passage, is the provision of a favorable .approach of the Huid to the aperture, and consequently the initiation of conditions favorable to the'maintenaace of substantially straight How throu the aperture; straight meaning at all` points parallel with the surfaces of thel valve-members.

ln the drawings hereto annexed, which. villustrate the structure and inode of operationof a throttling valve in and 'by which Mld a compromise is effected between the theoretically conflicting requirements above alluded to,

Figure 1 shows-partly throttling valve, and

Figure 2 is a diagram illustrating the principles by. which the proper proportions of a throttling valve may empirically be determined.

The valve-casing, the valve operating stem, land other adjuncts illustrated' in the draw-` ings may be of any usual or convenient form, and need 'not be described in detail. The closuremember or plug of the valve, presently to be described in detail,`will prefer# ably be loosely attached lto the operating v stem, so as to be self centering in the aperturewhich it controls and closes;

The factors with which this invention is particularly concerned are the valve closure member 1 and the surrounding seat 2. The valve will be placed so that H and L are, respectively the high and\low pressure sides of the valve apparatus, iow therefor, being from H through the valve aperture .t L.

ln order to provide for a large differenin' section-'a tial in fluid pressure as between H and L,

the annular passage formed by the members vv1 and 2 should be so proportioned as to provide as large a difference as is practically 'I expedient, between the 'minor diameter of the annular passage. at the intake, or high pressure end, and the major diameter at the outlet or low pressure end.

Theoretically, the maximum difference between intake a erture capacity and deliveryv aperture capacity, would be produced by a flat disc closure covering an aperture in a at plate; practically this would be far` from admissible, because of the abrupt change invdirection of flow from the plate v aperture linto the expansion aperture, which would involve sharp impingement of the moving uid against the-surface of the closure'mem'ber, and next against the opposing surfacekof the plate; erosion of the materials of which the closure and .its seat are composed would promptly develop, and the initial elic'acy of such a contrivance,both as a throttling valveand as a closure would be destroyed. Thus the rovision by proportions of the closure and) its cooperating seat, for adequate expansion within the aperture 'mustbe governed by the consideration of substantially straight low into,l through, and out of the aperture. i

Considermg a theoretical limit Vin the i other direction; an annular cylindrical aperture would provide forI straightrfiow, but would be a contri-vanceill adapted to allow the desired expansion and decline of pressure, within workable proportions. I

A satisfactory reconciliation between the conicting requirements of straight flow and adequate expansion Iin the throttling aperlaperture least and greatest aperture area, and that 'about thirty degrees. The ratio between the minor diameter of the annular conical aperture, at.5 to the major diameter thereof at 6, is approximately 1:2; 4thus the ratio of aperture areas at these two diameters is approximately 1 :4.- I have ascertained empirically, that in order to obtain freedom from erosion in a valve apparatus characterized by an aperture of the taper here shown, the minor and major aperture areas should have a ratio'of value not greater than 1-: 2.25. .But it has further been ascertained, that erosion will not be obviated by the observance of this maximum ratio-value alone, since provision must also be made for a substantially unidirectional travel of expanding fluid, in substantial parallelism with the closely adjacent surfaces of the valve members, which constitute the walls of the aperture. This factor of compromise is secured by a pair of mutually fitting conical members (1 and 2) having an angle of conicity such that, while the ratio between minor 'and major aperture areas remains within the value i12-5 the major diameter of the diameters, not in excess of in value.

Structurally, the valve apparatus will be improved by extending the conical surface of the member 1, as at 3, beyond the minor aperture-diameter, by rounding the apex of the member 1, as at 4, and by rounding` the edge of the seat member 3 at the minor aperture-diameter or edgeof intake to the aperture.A The extension of the conical surface of the member 1, at 3 preserves the generally parallel relation between the surfaces of members 1 and 2 as the member 1 is moved to produce the annular conical Bearing in mind that is the `maximum practical limit of ratio value between is the 'maximum l praaictical limit of ratio value between major diameter of annular aperture and axial length of aperture, if the conflicting requirements of adequate expansion and straight flow in the aperture are to be reconciled to practical conditions, the

variations or developments of valvev proportionswithin these limits, and with reference to the high pressures to be reduced or throttled, and the low pressures to be maintained, may now be discussed.

. The variable factors now to be considered are the absolute high pressure, and the prelaatse we assume that a pressure of only one pound above atmospheric is to be maintained on the low pressure side of the throttling valve, the reduction to this pressure value with a valve closure and seat of the conical angle prescribed by the limits above mentioned, will be accomplished as the datum of high pressure increases in value, by extending the axial length between the minor and major diameters oi the conical members. 'lhe maximum ratiovalue prescribed above, as between minimum and maxium aperture areas involves a valve closure and seat having a conical angle of about thirty degrees. Given a valve apparatus proportioned to v these maxima of ratio value, it will be found that the slight opening employed for throttling will produce aboutone pound pressure on the low pressure side, if the high pressure stands at about two hundred pounds. To construct a. similar valve to throttle higher pressures down toone pound, all that is necessary is to extend the conical valve members at their major diameter ends, thus reducing the ratio values belowl the maxima em irically determined and above stated,

eferring to Fig. 2, which shows in dia-l grain the elements of the valve; A is the geomtrical apex of the cones and a, b, o, d, e, f, are successively increasing major diameters. rl`he arrows indicate the straight flow with which it is desired to have the luidjet emerge from the annular aperture, without helling and thus setting up erosions both at the delivery end of the aperture and within it to a greater or less extent. lf the major diameter at a provides the pro ortions proposed to secure this result and re uce steam pressure from 200 pounds to onelpound, valve closures and seat members proportioned as indicated by the major diameter positions at b, c, etc. wi lbe proper to produce a reduction to one pound from 3 pressures higher than 200, conserving the straight flow in and'from the a erture. ln all these successive proportions s own in the diagram, the values of the ratios, minimum aperature area to maximum aperture area, and major diameter to axial length, diminish asrthe axial length of the valve members, or rather of the conical aperture, increases.

The provision of a long conical surface of contact between the two valve members renders lthe closure of the valve secure and reliable. rl`hrottlin valves made according to the principles and prescriptions above set forth endure without deterioration for indefinite periods.

l. ln a throttling valve, the combination of mutually fitting conical closure and seat members adapted to form a frusto-conical annular passage for fluid, the said passage characterized by a ratio gf intake area to delivery area not substantially greater than axial length not substantially greater than the cone oit the closure member being extended from the smaller end of the aperture.

3. In a throttling valve', the combination of mutually fitting conical closure and seat members adapted to form a frusto-conical annular passage for Huid, the said passage characterized by a ratio ol intake areak to delivery area not substantially greater than axial length not substantially greater than and by a ratio of major diameter to the cone of the closure 'member being extended from the smaller end of the aperture and rounded at its extremity.

4f. ln a throttling valve, the combination of mutually fitting conical closure and seat members adapted to form a rustO-conical Y annular passage for fluid, the said passage characterized by a ratio ofintake area to delivery areaA not substantially greater than and by a ratio of major diameter to 2.25 axial length not substantially greater than ,27, the rim of the aperture at the smaller end` thereof being rounded. I

5. ln a throttling valve, the combination of mutually tting conical closure and seat members adapted to form a truste-conical annular passage for fluid, the said passage characterized by a ratio of intake area to delivery area not substantially greater than 55 axial, length not substantially greater than and by v a ratio of major diameter to 2f the cone of the closure member being extended from the smaller end of the aperture, and the rim of the aperture at the smaller end thereof-*being rounded.

Signed by me at Boston, Massachusetts, this eleventh day olf-May, 1923.

nnnvnv rr. winmsroet and by a ratio of major diameter to i lill ict 

